Carbon Emissions Caps · The most consequential building law in the US
LL97 sets declining carbon intensity limits on NYC buildings over 25,000 sq ft. Exceedances are billed at $268 per metric ton of CO2e per year — with caps stepping down sharply in 2030 and again in 2035.
How the caps work
Each covered property has an annual emissions budget based on occupancy group and gross floor area, expressed in kgCO₂e per sq ft. Actual emissions are calculated from LL84 benchmarking data using DOB-published emission coefficients.
- Coefficients by fuel: electricity, natural gas, steam, fuel oil
- Electricity coefficient declines as the grid decarbonizes
- Occupancy-weighted average for mixed-use properties
- Deductions available for verified DER, RECs (bounded), and offsets
2024–2029 vs 2030–2034
The 2024 caps are lenient — roughly 20% of covered buildings will exceed. The 2030 caps are severe — DOB projects that 75%+ of buildings without an intervention program will be non-compliant, with median annual fines in the six figures.
Compliance pathways
There are four legitimate ways to close the LL97 gap:
- Physical decarbonization — heat pumps, envelope, controls
- Operational efficiency — retro-commissioning, load management
- Beneficial electrification synchronized with grid decarbonization
- Bounded use of GHG offsets and clean DER credits
BES LL97 methodology
We run a deterministic, audit-trailed LL97 engine that outputs exposure by year through 2050 — with sensitivity to grid coefficient trajectory, capital plan sequencing, and financing structure.